LG ffh 8900 Diagram

4 (3)

SERVICING PRECAUTIONS

NOTES REGARDING HANDLING OF THE PICK-UP

1.Notes for transport and storage

1)The pick-up should always be left in its conductive bag until immediately prior to use.

2)The pick-up should never be subjected to external pressure or impact.

Storage in conductive bag

Drop impact

2.Repair notes

1)The pick-up incorporates a strong magnet, and so should never be brought close to magnetic materials.

2)The pick-up should always be handled correctly and carefully, taking care to avoid external pressure and impact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/or damage to the printed-circuit board.

3)Each and every pick-up is already individually adjusted to a high degree of precision, and for that reason the adjustment point and installation screws should absolutely never be touched.

4)Laser beams may damage the eyes!

Absolutely never permit laser beams to enter the eyes!

Also NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.

NEVER look directly at the laser beam, and don′t let contact fingers or other exposed skin.

5)Cleaning the lens surface

If there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as used for camera lens). The lens is held by a delicate spring. When cleaning the lens surface, therefore, a cotton swab should be used, taking care not to distort this.

Pressure

Magnet

Pressure

How to hold the pick-up

Cotton swab

Conductive Sheet

6)Never attempt to disassemble the pick-up.

Spring by excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab. (Do not use any other liquid cleaners, because they will damage the lens.) Take care not to use too much of this alcohol on the swab, and do not allow the alcohol to get inside the pick-up.

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NOTES REGARDING COMPACT DISC PLAYER REPAIRS

1.Preparations

1)Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). These components are sensitive to, and easily affected by, static electricity. If such static electricity is high voltage, components can be damaged, and for that reason components should be handled with care.

2)The pick-up is composed of many optical components and other high-precision components. Care must be taken, therefore, to avoid repair or storage where the temperature of humidity is high, where strong magnetism is present, or where there is excessive dust.

2.Notes for repair

1)Before replacing a component part, first disconnect the power supply lead wire from the unit

2)All equipment, measuring instruments and tools must be grounded.

3)The workbench should be covered with a conductive sheet and grounded.

When removing the laser pick-up from its conductive bag, do not place the pick-up on the bag. (This is because there is the possibility of damage by static electricity.)

4)To prevent AC leakage, the metal part of the soldering iron should be grounded.

5)Workers should be grounded by an armband (1MΩ )

6)Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to prevent static electricity changes in the clothing to escape from the armband.

7)The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.

Armband

		Resistor
	Resistor	(1 Mohm)
	Resistor	Conductive
	(1 Mohm)	Conductive
	(1 Mohm)	Sheet
		Sheet

CLEARING MALFUNCTION

You can reset your unit to initial status if malfunction occur(button malfunction, display, etc.).

Using a pointed object(such as driver), simply press the RESET button on the inside of the volume knob for more than 3 seconds.

If you reset your unit, you must reenter all its settings(stations, clock, timer)

NOTE: 1. To operate the RESET jump wire, pull the volume rotary knob and release it.

2. If you wish to operate the RESET jump wire, it is necessary to unplug the power cord.

VOLUME

VOLUME KNOB

RESET button

DOWN

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ESD PRECAUTIONS

Electrostatically Sensitive Devices (ESD)

Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components commonly are called Electrostatically Sensitive Devices (ESD). Examples of typical ESD devices are integrated circuits and some field-effect transistors and semiconductor chip components. The following techniques should be used to help reduce the incidence of component damage caused by static electricity.

1.Immediately before handling any semiconductor component or semiconductor-equipped assembly, drain off any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging wrist strap device, which should be removed for potential shock reasons prior to applying power to the unit under test.

2.After removing an electrical assembly equipped with ESD devices, place the assembly on a conductive surface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.

3.Use only a grounded-tip soldering iron to solder or unsolder ESD devices.

4.Use only an anti-static solder removal device. Some solder removal devices not classified as "anti-static" can generate electrical charges sufficient to damage ESD devices.

5.Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESD devices.

6.Do not remove a replacement ESD device from its protective package until immediately before you are ready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together by conductive foam, aluminum foil or comparable conductive materials).

7.Immediately before removing the protective material from the leads of a replacement ESD device, touch the protective material to the chassis or circuit assembly into which the device will by installed.

CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL OTHER SAFETY PRECAUTIONS.

8.Minimize bodily motions when handing unpackaged replacement ESD devices. (Otherwise harmless motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static electricity sufficient to damage an ESD device).

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ADJUSTMENTS

This set has been aligned at the factory and normally will not require further adjustment. As a result, it is not recommended that any attempt is made to modificate any circuit. If any parts are replaced or if anyone tampers with the adjustment, realignment may be necessary.

IMPORTANT

1.Check Power-source voltage.

2.Set the function switch to band being aligned.

3.Turn volume control to minimum unless otherwise noted.

4.Connect low side of signal source and output indicator to chassis ground unless otherwise specified.

5.Keep the signal input as low as possible to avoid AGC and AC action.

TAPE DECK ADJUSTMENT

1. AZIMUTH ADJUSTMENT

Deck Mode

Test Tape

Test Point

Adjustment

Adjust for

A Deck Playback

MTT-114

Speaker Out

DECK Screw

Maximum

B Deck Playback

MTT-114

Speaker Out

Azimuth Screw

Maximum

Electronic

Dual-trace

Voltmeter

synchroscope

Head

Playback Mode

Speaker Out

L ch

L out

CH1 CH2

Test Tape

Unit

MTT-114

R ch

GND

R out

Figure 1. Azimuth Adjustment Connection Diagram

2. MOTOR SPEED ADJUSTMENT

Deck Mode	Test Tape		Test Point		Adjustment	Adjust for	Remark

Normal Speed	MTT-111		Speaker Out		VR201	3kHz ± 1%

Hi-Speed	MTT-111		Speaker Out		more than 5.4kHz		High-Speed Dubbing Mode

	Head				Speaker Out	Frequency Counter
			Playback Mode
Test Tape				L out
Test Tape			Unit
MTT-111


		Record/Playback		R out
		Record/Playback			GND

head

Figure 2. Motor Speed Adjustment Connection Diagram

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3. RECORD BIAS ADJUSTMENT

Deck Mode

Test Tape

Test Point

Adjustment

Adjust for

Rec/Pause

MTT-5511

ERASE HEAD Wire(PN202)

L203

90kHz±5kHz

Head

Record/Playback

PN202

Frequency Counter

and Pause Mode

Test Tape

Unit

MTT-5511

Record/Playback

GND

head

Figure 3. Record Bias Adjustment Connection Diagram

4. TUNER ADJUSTMENT

Item

Test Point

Adjustment

Adjust for

DC Voltage

Checker Pin TP1, TP2

L106

0V±50mV

FM Antenna	Electronic
FM Antenna	OSCILLOSCOPE
Terminal	Speake
Signal Generator
	Unit
GND

Figure 4. Tuner(S curve) Adjustment Connection Diagram

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TROUBLESHOOTING

Turn power on.

Is power on?

YES

Does initial read work?

YES

Does it play?

YES

Does it output audio?

YES

Check power supply circuit. (Check PN 701)

Check laser circuit.

Check focus circuit.

Check disc.

Check tracking servo circuit.

Check audio circuit.

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Fails to initial read

		NO		NO	A
	Disc motor turns.		Does laser light?	NO



			YES		B
YES			YES

Does RF

Does tracking

waveform

servo work?

appear?

Lower envelope

TP 801(RF)

of TP801(RF)

waveform is flat.

1.3V

YES

Is rotation normal?

YES

Is there no dropout of RF signal?

YES

Does signal

Does TE2 signal

appear at

appear at pin 53

Defective IC

TP801(TEO)?

of IC801?

801, pick up

and/or open

wire.

YES

Detective pattern.

Does signal appear at IC 803

Defective IC 801

Pin 26 and Pin 27 ?

and/or IC 803

YES

Defective pick-up

and/or connector.

Does GFS (IC802 pin [)

Defective IC 801.

show as below?

Scratch in disc initial read area.

Defective pick-up adjustment focus offset.

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A	Laser does not light.

Is “3.5V” applied to pin 70 of IC 801?

YES

Did pickup return to

Is data transferred from

Defective MICOM.

innermost circular?

MICOM IC ?

YES

Does voltage appear at IC

803 pin , ?

Defective IC 801, 803

YES		Defective slide motor and/or
		connector.
		connector.

Does it stop at inner pick

Is defect output from LM

circular after shift?

SW applied to pin of

YES

PN803?

Defective LMT SW and/or

connector.

OPEN

YES

Defective MICOM.

YES

Is power supplied to laser Q801?

Defective connector.

(Q 801 collector: about 1.8V)

R801 1.0V

YES

Defective Q 801 and/or laser.

YES

Does laser current flow?

YES

R801 1.0V

Defective laser and/or

1.0V across R801

connector.

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B	Laser lights.

Does lens move up/down?

YES

Confirm	Does TP 801 RF signal appear even in
initial	low level?
read with
disc

	YES

	Is laser output adjustment correct?
	Is laser output adjustment correct?

YES

Does FOK(focus ok) signal appear?

TP801

(RF)

IC801 pin 40 (FOK)

YES

Does IC 801 out focus search signal?

IC 801 pin 48 (FEO)

YES

Is focus search signal applied to pin 13 , 16 of CN801?

YES

Defective IC801

Defective IC803

Open activator and/or connector.

NO	Open connector and/or
	defective IC 801.

NO	Incorrect turntable height.
	Degraded laser diode.

Defective IC 801.

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